1. Field of the Invention
This invention relates to seals and to well pipe suspension apparatus having novel sealing means.
2. Description of the Prior Art
Various means have heretofore been used to seal around pipe hangers in a wellhead as, for example, the O-rings and packing elements of elastomeric material as shown in U.S. Pat. No. 2,830,665 Burns et al. Recently, however, oil wells having bottom hole pressures of as high as 30,000 pounds per square inch have been encountered, and such seals as have previously been used have not been capable of holding such pressures.
Metal-to-metal seals of various kinds have also been used in many installations, including in wellheads. For example, the aforesaid patent to Burns et al shows the use of a metal ring gasket between two flanges of the christmas tree construction shown there.
One form of metal-to-metal gasket which has heretofore been known is that shown in U.S. Pat. No. 2,992,840 to Reynolds et al, which discloses a metal gasket which is frusto-conical in cross section and which is compressed between two flanges having a greater cone angle so that the gasket is deformed, the edges of the gasket being "coined" so as to closely engage elements of the flanges and provide a metal-to-metal seal.
Gaskets which apparently function similarly to those shown in the Reynolds et al patent are manufactured and sold by Aeroquip Corporation of Los Angeles, California under the trademarks CONOMASTER and CONOSEAL.
None of the aforesaid sealing systems has been capable of dependably providing a seal under pressures as high as 20,000 psi, much less 30,000 psi or higher. Furthermore, sealing systems such as that shown in the Reynolds et al patent are objectionable because the gaskets may work-harden and cause damage to sealing surfaces, and do not dependably seal against pressures from either direction, as required in pipe suspension apparatus, and because of difficulty in installing such a gasket in a well pipe suspension apparatus, where the gasket must be installed in an inaccessible location.